| 摘要 |
<p>A flexible non-metallic, corrosion-resistant conduit (2) for a cable assembly which includes an extruded tubular synthetic plastic liner portion (4) having on is outer surface a plurality of circumferentially spaced helical strengthening ribs (8), and an extruded tubular synthetic plastic sleeve (10) portion extending concentrically about the liner portion. According to the method of the present invention, as the liner portion (4) is extruded via a first die, it is longitudinally pulled and rotatably twisted about its longitudinal axis to impart the desired helical configuration to the ribs (8). In one embodiment, the sleeve portion (10) is extruded by a second die concentrically about the liner (4), thereby to fill the spaces between the ribs (8), and in a second embodiment, the sleeve portion (20) is simultaneously formed by the first die integrally with the tips of the ribs (18), thereby to define helical passages (23) between the ribs. According to a third embodiment, an intermediate synthetic plastic layer (35) is extruded on the liner prior to the formation of the sleeve (40) and in a fourth embodiment, at least one reinforcing filament layer (59) is wound on the liner prior to the formation of the intermediate layer (55).</p> |
